During fabrication of optical and/or electrical communication systems, it is often desirable to precisely measure positions of adjacent components relative to one another and/or adjust such positions to achieve a desired orientation. For instance, it is advantageous to precisely align edge surfaces of integrated optical devices with other components, such as optical fiber array connectors for forming interconnections with relatively low insertion loss. However, conventional alignment techniques are crude and produce inconsistent results in forming low insertion loss interconnections.
More specifically, integrated optical devices are typically implemented as silica optical circuits having a layer of SiO.sub.2 formed on a surface of a substrate, such as a silicon substrate, with integrated silica optical waveguide structures formed within the SiO.sub.2 layer. Waveguides used for providing light signals to and/or from external components extend to an edge surface of the device. The basic structure of such devices is described in C. H. Henry et al., "Glass Waveguides on Silicon for Hybrid Optical Packaging", 7 J Lightwave Technol., pp. 1530-1539 (1989), which is incorporated by reference herein. Integrated optical devices advantageously enable the implementation of a variety of optical circuits, such as filters, couplers, switches in a compact device at relatively low fabrication cost.
An interconnection between an integrated optical device and an optical fiber array connector is typically formed by aligning and butt-coupling such components in the following manner. Respective optical fibers are secured in grooves of a V-groove substrate to form the array connector. Separations between grooves of the substrate are positioned to correspond to separations between the optical waveguide ends at the integrated optical device's edge surface. The optical fibers are secured in the V-groove substrate with their ends substantially flush with an edge surface of the substrate. These fiber ends and the integrated optical device edge surface are then polished.
The respective connector and integrated optical device edge surfaces are then brought into physical contact with one another typically to achieve alignment. Then, the device and connector are backed off from one another in a direction normal to the adjacent edge surfaces to a distance on the order of 10 .mu.m. The resulting gap between the aligned facing surfaces of the device and connector is then filled with a UV or heat cured epoxy to connect the components.
However, consistently producing low insertion loss interconnections of less than 0.2 dB in such a manner has been problematic and difficult to achieve. Such interconnect methods have often produced interconnections with undesirably high insertion loss on the order of 0.5 dB. Such relatively high insertion loss is often attributable to scratching or chipping of the optical fiber ends when the fiber array connector is brought into contact with the integrated optical device edge surface. Also, the step of backing off the components from one another often causes the facing device and connector surfaces to lose their parallel alignment. Such misalignment disadvantageously causes an increase in insertion loss of subsequently formed interconnections.
As a consequence, there is a recognized need for enhanced techniques for measuring and/or setting the relative positions of adjacent components that is useable for consistently achieving optical component interconnections with reduced signal loss.